1. Field of the lnvention
The present invention relates generally to an apparatus for automatic mounting of components on printed circuit boards and, more particularly, to an apparatus for supplying components to a printed circuit board equipping head.
2. Description of the Related Art
German Patent Document 34 05 971 discloses an apparatus for equipping printed circuit boards with radially wired components. Cross bars arranged at identical spacings from one another in an endlessly circulating ladder-shaped drive pick up the components from a feeder device arranged along the endless drive at the same spacing. The components are conveyed by the endless drive to a transfer position in which an equipping head grasps the component and positions it at the appropriate equipping position on a printed circuit board. The endless drive is advanced in a clock fashion and the spatial distribution of the feeder devices and the equipping head are matched to one another so that a cross bar of the ladder-shaped drive is allocated to every feeder device and to the equipping head at every clock cycle.
German Patent Document 32 31 174 discloses an apparatus for equipping printed circuit boards with wired components in which an endlessly circulating chain carries pallets arranged at uniform spacings from one another. These pallets pick up components from a feeder arranged along the chain in the same spacing and convey them to a transfer position. An equipping head formed as a turret having a plurality of gripping elements picks up a component and positions it at an appropriate equipping position on a printed circuit board. The clocked advance of the endless chain and the spatial distribution of the feeder devices and the equipping head are matched to one another so that one of the pallets is allocated to each feeder means and to the equipping head after every clock cycle.
The known devices, thus, teach the simultaneous approach and operation of the conveying elements at the two component transfer positions. In the known apparatus for equipping printed circuit boards, division errors in the spacing between the conveying elements can arise due to stretching of the endless drive which is used for conveying the components. This stretching prevents an exact simultaneous approach of the retrieving position of the component feeder devices and of the transfer position of the equipping head by the component conveying devices and also prevents, or at least considerably deteriorates, the reliable transfer of the component therebetween. In other words, when the receiving position is reached by one of the conveying elements on the endless drive, the other conveying element may not be aligned accurately with the transfer position but instead may be slightly out of alignment so that faulty transfer of the component occurs.